In a conventional record player the pivotable tone arm and its stylus or needle or cartridge is driven inwardly across the record as the record rotates. The path that the stylus end of the tone arm describes is a circular arc and that arcuate path causes the stylus to engage the groove at a slightly different angle on each rotation of the record, resulting in undesirable distortion. To eliminate this distortion the stylus end of the tone arm should trace a linear, radial path across the groove, thereby engaging the groove tangentially on each rotation. This imitates the linear manner in which record grooves are cut as disclosed in U.S. Pat. No. 4,135,772 and the references cited therein.
Typically in conventional linear tracking devices, the tone arm is controlled by an electric, electronic, photoelectric or other device. Such tracking mechanisms are complex, expensive, and subject to electrical failure. Further, these tone arms operate to maintain a linear path only after the stylus has deviated from such a path; e.g., instead of maintaining a perfect linear alignment they merely correct continuous deviations by pulling the stylus back into linear alignment.
Purely mechanical devices for linearly tracking the groove of a photograph record have been developed. However, some of these, such as U.S. Pat. No. 3,940,149, also correct alignment deviations only after they occur and thus experience the same problem as comparable electric and electronic devices. Alternatively, mechanical tracking devices have been produced which prevent such deviations. However such devices, as U.S. Pat. No. 2,676,808, were designed for use with older and heavier tone arm devices that have largely been replaced by extremely lightweight devices which apply to the record groove less than one tenth the stylus force as did the older cartridges, thus reducing record wear and producing a higher accuracy of sound reproduction (high fidelity). However, the high rolling friction of such linear tracking devices is too great for present lightweight tone arm devices.